Effect of Grain Refinement and Metal Oxide Dispersions on High-Temperature Oxidation Resistance of Nickel Aluminide Coating
PENG Xiao1,2, TIAN Lixi1, ZHANG Bangyan1, WANG Xiaolan2, DONG Zhihong2
1. Institute of Corrosion and Protection, School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063, China;
2. Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
NiAl coating obtained by pack aluminization is the firstly used as Al2O3-forming high-temperature coating. Since the middle of the last century, NiAl coatings were employed in hot sections of aero-engines for protection against high temperature oxidation. Investigations of the oxidation mechanisms of the coating, and exploration of the coating techniques continue up to now. On a basis of understanding to the oxidation mechanism of alloys and thermal growth of Al2O3, a concept of improving the oxidation resistance of nickel aluminide coating by means of grain refinement and typical metal oxide dispersions has been proposed. Meanwhile a method to refine the grains of the nickel aluminide coating and disperse it with metal oxide nanoparticles has been presented, and key factors (including growth rate of the Al2O3 scale, Al2O3 phase transformation from metastable phases to the stable phase, the Al2O3 adhesion to the coating as well as the interdiffusion between the coating and the metal substrate) intrinsically correlated with the oxidation resistance of the coating which can be significantly affected by its modification in microstructure and chemical composition have been reviewed. The new result is expected to be helpful to further offer theoretical and experimental bases for tapping the potential and prolonging the service life of the aluminized coatings in application.